The development of non-invasive electrophysiological techniques applicable for routine evaluation in humans of peripheral and brainstem auditory neural activity has provided a powerful tool for the investigation of normal and abnormal auditory system functioning. Brainstem activity recorded via surface EEG electrodes reveals responses reflecting both transient and sustained neural activity to sounds. To date, extensive study has been carried out on the transient neural responses, the brainstem evoked potential (BEP). Its value in clinical assessment of the peripheral and brainstem auditory neuraxis has been well established. Studies of the brainstem evoked activity to sustained sounds, the frequency-following potential (FFP) have been a more preliminary nature. The proposed study will carefully evaluate the FFP in normal-hearing and hearing-impaired subjects. The objective is to determine the response characteristics of the FFP so that it may be systematically applied to evaluation of aspects auditory functioning not revealed by other procedures. The long range goal of the proposed research is to develop a thorough understanding of the scalp-recorded FFP and its underlying neurophysiological mechanisms. In this way, it may be possible not only to more validly assess auditory dysfunction, but also to better understand the effects of auditory dysfunction on brainstem neural activity.